The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing charge enhancing additives which impart or assist in imparting a positive charge to the toner resin particles and enable toners with rapid admix characteristics, and wherein there is selected as the primary toner pigment a magnetite, especially an acicular magnetite, and which magnetite is available from Magnox, Inc., Wilmington, Del., and wherein the toner contains certain toner additives. In embodiments of the present invention, there are provided toners comprised of resin particles, magnetite particles, pigment particles of carbon black, charge enhancing additives, such as those comprised of the salts of RHODAMINE 6G .TM. such as the silico molybdate salt of RHODAMINE GG .TM. available as FANAL PINK 4830.TM. from BASF Corporation, Clifton, N.J., pigments such as carbon black, wax, and surface additives of silica, especially fumed silicas available from Wacker Chemicals, or alumina; and magnetite. The addition of magnetites, such as soft magnetites like MAPICO BLACK.RTM., to the surface of the magnetic toner, especially a MICR toner eliminates, minimizes, or reduces the formation of undesirable comets including especially comet formation on photoconductive imaging members, including flexible layered imaging members as illustrated, for example, in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. In embodiments of the present invention, the magnetite is added to a toner containing magnetite during, for example, the preparation thereof, such as during the melt mixing toner processes and wherein the magnetite functions primarily as a lubricant. The toner compositions of the present invention in embodiments thereof possess excellent admix characteristics, maintain their triboelectric charging characteristics for an extended number of imaging cycles, and enable the elimination or minimization of undesirable comets on the imaging member or photoconductor. Developers of the present invention are comprised of the aforementioned toners and carrier particles, especially carrier particles comprised of a core with a mixture of polymers thereover. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes, and preferably magnetic image character recognition processes (MICR), such as processes similar to those selected for the Xerox Corporation 8790/9790 MICR machines, and preferably the Xerox Corporation 4135.RTM. MICR test fixture or machine, and wherein personal checks with no, or minimal comets can be generated.
Toner and developer compositions with wax and certain surface additives, such as silicas, KYNAR.RTM., or metal oxides, are known. Illustrated, for example, in U.S. Pat. No. 3,900,588 is a toner with surface additive mixtures of silica or strontium titanate and polymers like KYNAR.RTM., see column 7, lines 12 to 17. This patent discloses, for example, a toner with a minor amount of a polymeric additive like KYNAR.RTM., and a minor amount of an abrasive material, such as silica, like AEROSIL R972.RTM.. Toners and developers with surface additives of metal salts of fatty acids like zinc stearate and silica are known, reference for example U.S. Pat. Nos. 3,983,045 and 3,590,000. In U.S. Pat. No. 4,789,613, there is illustrated a toner with an effective amount of, for example, strontium titanate dispersed therein, such as from about 0.3 to about 50 weight percent. Also disclosed in the '613 patent is the importance of the dielectric material with a certain dielectric constant, such as strontium titanate, being dispersed in the toner and wherein the surface is free or substantially free of such materials. Further, this patent discloses the use of known charge controllers in the toner, see column 4, line 55, olefin polymer, see column 5, line 35, and a coloring agent like carbon black as a pigment. Treated silica powders for toners are illustrated in U.S. Pat. No. 5,306,588. Toners with waxes like polypropylene and polyethylene are, for example, illustrated in U.S. Pat. Nos. 5,292,609; 5,244,765; 4,997,739; 5,004,666 and 4,921,771, the disclosures of which are totally incorporated herein by reference. Magnetic toners with low molecular weight waxes and external additives of a first flow aid like silica and metal oxide particles are illustrated in U.S. Pat. No. 4,758,493, the disclosure of which is totally incorporated herein by reference. Examples of metal oxide surface additives are illustrated in column 5, at line 63, and include strontium titanate. Single component magnetic toners with silane treated magnetites are illustrated in U.S. Pat. No. 5,278,018, the disclosure of which is totally incorporated herein by reference. In column 8 of the '018 patent, there is disclosed the addition of waxes to the toner and it is indicated that surface additives, such as AEROSIL.RTM., metal salts of fatty acids and the like, can be selected for the toner. Magnetic image character recognition processes and toners with magnetites like MAPICO BLACK.RTM. are known, reference for example reissue U.S. Pat. No. 33,172, the disclosure of which is totally incorporated herein by reference, and U.S. Pat. No. 4,859,550. The 33,172 patent also discloses certain toners with AEROSIL.RTM. surface additives. The toners and developers of the present invention may in embodiments be selected for the MICR and xerographic imaging and printing processes as illustrated in the 33,172 patent.
Moreover, toners with charge additives are known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions. There are also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica.
Also, there is disclosed in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there are disclosed in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other documents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; 4,394,430 and 4,560,635 which illustrates a toner with a distearyl dimethyl ammonium methyl sulfate charge additive.
Moreover, toner compositions with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. No. 4,404,271 a complex system for developing electrostatic images with a toner which contains a metal complex represented by the formula in column 2, for example, and wherein ME can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives. Further, TRH as a charge additive is illustrated in a number of patents, such as U.S. Pat. No. 5,278,018, the disclosure of which is totally incorporated herein by reference.
Toners with FANAL PINK.RTM. charge additives appear to be illustrated in U.S. Pat. Nos. 5, 158,851 and 5,166,026, the disclosures of which are totally incorporated herein by reference. These patents appear to disclose FANAL PINK.RTM., a rhodamine salt, as charge control agent for toners with a multiblock binder resin ('851 patent) and for semicrystalline olefin binder resin based toners ('026 patent). Also, U.S. Pat. No. 4,268,599 appears to indicate the use of RHODAMINE B.RTM. as a component for coating carrier to control charge to mass ratio on the carrier. BASF European publication EP 392356-B1 (90-314079/42) illustrates xanthene dyes, such as RHODAMINE.RTM., in electrophotographic toners.
The disclosures of each of the patents mentioned herein are totally incorporated herein by reference.
Disclosed in copending patent application U.S. Ser. No. 299,875, the disclosure of which is totally incorporated herein by reference, is a single component toner comprised of resin particles, magnetite treated, or coated with a phosphate titanium component wax, and surface additives comprised of mixtures of silicas and strontium titanate.
Disclosed in copending patent applications U.S. Ser. No. 331,444, and U.S. Ser. No. 331,441, the disclosures of which are totally incorporated herein by reference, is a toner comprised of resin particles, magnetite, carbon black, rhodamine charge additive, wax, and a surface mixture of silica, strontium titanate and polyvinylidene fluoride, and wherein comets are eliminated or minimized.